1. Field of the Invention
The present invention relates to a low boron amorphous alloy having excellent soft magnetic characteristics, and more specifically to a low boron amorphous alloy in which the boron content is advantageously reduced without deteriorating the magnetic characteristics of the alloy.
2. Description of the Related Art
Various Fe-Si-B alloy compositions are known to possess excellent soft magnetic characteristics.
For example, U.S. Pat. No. 3,856,513 discloses an amorphous alloy containing at least 80 at % Fe, at least 10 at % B and no more than 6 at % Si. Further, U.S. Pat. No. 235,064 discloses an amorphous alloy composed of 77-80 at % Fe, 12-16 at % B and 5-10 at % Si.
Almost all known Fe-Si-B amorphous alloys contain at least 10 at % B, as B is very important to the amorphous property of such alloys. The higher the B content, the stronger the amorphous forming capability of the alloys, whereby thermal stability is improved. Thus, it has been conventionally believed that a B content of at least 10 at % is required to produce excellent soft magnetic characteristics in Fe-Si-B amorphous alloys.
Further, both iron loss and magnetic flux density of conventional Fe-Si-B amorphous alloys containing less than 10 at % B are inferior to alloys containing at least 10 at % B.
Because of the high cost of B, there have been attempts to improve Fe-Si-B amorphous alloys containing less than 10 at % B. For example, C has been added to stabilize age deterioration and to improve amorphous property forming capabilities (Japanese Patent Unexamined Publication No. 57-145964 (1982) and Japanese Patent Unexamined Publication No. 58-42751 (1983)), Mn has been added to improve surface treatment properties (Japanese Patent Unexamined Publication No. 61-136660 (1986), and Cr has been added to improve casting properties (Japanese Patent Unexamined Publication No. 58-210154 (1983)). However, maintaining excellent soft magnetic characteristics in Fe-Si-B alloys containing less than 10 at % B has not been accomplished in the art.